CN109455917B

CN109455917B - Method and apparatus for reducing residual stress of glass substrate

Info

Publication number: CN109455917B
Application number: CN201810783613.5A
Authority: CN
Inventors: 八幡惠辅; 小田晃一; 村上政直
Original assignee: Mitsuboshi Diamond Industrial Co Ltd
Current assignee: Mitsuboshi Diamond Industrial Co Ltd
Priority date: 2017-09-06
Filing date: 2018-07-17
Publication date: 2022-09-06
Anticipated expiration: 2038-07-17
Also published as: TWI772476B; JP2019043823A; KR20190027309A; TW201912596A; CN109455917A; JP7037167B2

Abstract

A method and apparatus for reducing residual stress of a glass substrate, which can reduce residual stress of a glass substrate formed integrally with a resin or the like. A method for reducing residual stress of a glass substrate (G) has a laser irradiation step in which heating is performed by irradiating each of a plurality of places in a portion of the glass substrate (G) where residual stress is high with laser light for a predetermined time.

Description

Method and apparatus for reducing residual stress of glass substrate

Technical Field

The present invention relates to a method for reducing residual stress of a glass substrate and an apparatus for reducing residual stress of a glass substrate.

Background

In order to cut the glass substrate into product sizes, a scribe line is formed on the glass substrate by a cutter wheel, and then the glass substrate is bent to cut the glass substrate along the scribe line (for example, see patent document 1).

However, residual stress remains in the score line due to the force applied by the cutter wheel blade and the stress applied during cutting. Therefore, horizontal cracks are likely to naturally occur on the surface of the glass substrate, and the cracks grow further due to moisture or the like with the passage of time.

Further, a technique of improving the strength of the end face of a glass substrate by irradiating the end face (edge) of the glass substrate with a laser beam to perform fusion rounding is known (for example, see patent document 2). In the fusion rounding, fine cracks at the substrate edge are eliminated, and the end face strength is improved.

However, in this method, residual stress is generated in the vicinity of the melted portion. In addition, the possibility of substrate breakage due to residual stress is increased. Specifically, the possibility of growth of internal defects with time and the possibility of breakage due to subsequent scratches increase, and when the residual stress is large, breakage may occur within several tens of minutes.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 6-144875

Patent document 2: japanese patent No. 5245819

Disclosure of Invention

Technical problems to be solved by the invention

In view of the above problems, methods of reducing residual stress of the edge of a glass substrate have been developed according to the prior art. For example, in a method of reducing the residual stress of the glass substrate, slow cooling is performed after temperature elevation. Specifically, first, the entire glass substrate is uniformly heated to a temperature higher than the glass transition point, then, it is held for a certain period of time, and finally, it is slowly cooled to normal temperature. In general, the heating, holding, and slow cooling steps take several hours or more.

In this method, there is an advantage in that the residual stress of the edge of the glass substrate can be almost completely removed. In addition, there is an advantage that a plurality of glass substrates can be simultaneously processed in the furnace.

However, since the entire substrate is heated to a temperature higher than the glass transition point, it cannot be applied to a glass product formed integrally with a material having low heat resistance such as resin. Fig. 32 shows a glass product in which resin materials P1 and P2 are integrally formed on a glass substrate G.

In addition, since a single residual stress reduction treatment takes several hours or more, it is impossible to reduce the residual stress immediately after the residual stress is generated. Therefore, it is difficult to apply the glass substrate having a high probability of breakage in several ten minutes due to a high residual stress.

A first object of the present invention is to reduce residual stress of a glass substrate formed integrally with a material having low heat resistance, such as resin.

A second object of the present invention is to reduce residual stress before breakage occurs even for a glass substrate in which breakage occurs within several tens of minutes in general due to high residual stress.

Means for solving the problems

In the following, various modes are described as means for solving the problems. These modes can be arbitrarily combined as needed.

A method for reducing residual stress of a glass substrate according to an aspect of the present invention includes the following steps.

The laser irradiation step of irradiating each of the plurality of places in the portion of the glass substrate where the residual stress is high with the laser for the predetermined time to perform heating.

According to this method, since the portion of the glass substrate having high residual stress is heated, the residual stress of the glass substrate formed integrally with a material having low heat resistance such as resin can be reduced. This is because the entire glass substrate is not heated, and thus the resin or the like is not easily affected by heat.

Further, according to this method, since the residual stress is reduced in the heating zone by heating the glass substrate for about 1 picosecond to 100 seconds, even for a glass substrate in which breakage occurs in usually several tens of minutes, the residual stress can be reduced before the breakage occurs.

The "portion where the heating residual stress is high" means that there is a portion of the glass substrate that is not heated.

The term "reduce the residual stress" means to reduce the residual stress to such an extent that the growth of internal defects with time is suppressed and the glass substrate to which the external force is not applied is not broken within a predetermined time.

In the laser irradiation step, a plurality of laser beams may be simultaneously irradiated to a plurality of places.

According to this method, the residual stress can be reduced in a short time.

In the laser irradiation step, laser irradiation may be performed sequentially at different positions.

According to this method, for example, simultaneous irradiation of a plurality of laser beams is repeated at different places. As a result, the area irradiated with the laser light increases, and the area of the area where the residual stress can be reduced increases.

The residual stress reduction device for a glass substrate according to another aspect of the present invention includes a laser device.

The laser device performs heating by irradiating each of a plurality of places in a portion of the glass substrate where the residual stress is high with laser light for a predetermined time.

According to this device, since the portion of the glass substrate having high residual stress is heated, the residual stress of the glass substrate formed integrally with a material having low heat resistance, such as resin, can be reduced. This is because the entire glass substrate is not heated, and thus the resin or the like is not easily affected by heat.

Further, according to this apparatus, since the residual stress is reduced in the heating zone by heating the glass substrate for about 1 picosecond to 100 seconds, even for a glass substrate in which breakage occurs in usually several tens of minutes, the residual stress can be reduced before the breakage occurs.

The laser device may irradiate a plurality of laser beams simultaneously to a plurality of places.

According to this device, the residual stress can be reduced in a short time.

The laser device may sequentially irradiate laser light to different positions.

According to this apparatus, for example, simultaneous irradiation of a plurality of laser beams is repeated to different places. As a result, the area irradiated with the laser light is increased, and the area of the region where the residual stress can be reduced is increased.

Effects of the invention

According to the present invention, the residual stress of the glass substrate formed integrally with a material having low heat resistance such as resin can be reduced. This is because the entire glass substrate is not heated, and thus the resin or the like is not easily affected by heat. Further, according to the present invention, even for a glass substrate in which breakage occurs within usually several tens of minutes due to high residual stress, the residual stress can be reduced before breakage occurs. This is because the residual stress can be reduced in the heating region by heating one or more portions of the glass substrate for about 1 picosecond to 100 seconds and performing the heating once or a plurality of times with the heating positions shifted.

Drawings

Fig. 1 is a schematic view of a laser irradiation apparatus according to a first embodiment of the present invention.

Fig. 2 is a schematic view of a glass substrate showing movement of a laser spot.

Fig. 3 is a cross-sectional photograph of a fusion-rounded glass substrate.

Fig. 4 is a graph showing a change in phase retardation from the end face toward the middle side of the molten rounded glass substrate.

Fig. 5 is a schematic view of a glass substrate showing movement of a laser spot.

Fig. 6 is a schematic diagram of a glass substrate showing movement of a laser spot.

Fig. 7 is a schematic diagram of a glass substrate showing movement of the laser spot.

Fig. 8 is a schematic view of a glass substrate showing movement of a laser spot.

Fig. 9 is a schematic plan view showing a change in the shape of the laser spot.

Fig. 10 is a schematic plan view showing a change in the shape of the laser spot.

Fig. 11 is a schematic top view showing a variation in the shape of the laser spot.

Fig. 12 is a schematic plan view showing an example of the sequence of heating positions.

Fig. 13 is a schematic plan view showing an example of the sequence of heating positions.

Fig. 14 is a schematic view of a laser irradiation device according to a modification of the first embodiment.

Fig. 15 is a schematic view of a glass substrate showing the movement of the laser spot of the second embodiment.

Fig. 16 is a schematic view of a glass substrate showing movement of a laser spot.

Fig. 17 is a schematic view of a glass substrate showing movement of a laser spot.

Fig. 18 is a schematic diagram of a glass substrate showing movement of a laser spot.

FIG. 19 is a schematic plan view showing changes in the shape and the interval of heating regions.

FIG. 20 is a schematic plan view showing changes in the shape and interval of heating regions.

Fig. 21 is a schematic diagram showing branching of a laser spot using a diffractive optical element or a transmissive spatial light modulator.

Fig. 22 is a schematic diagram showing branching of a laser spot using a reflective spatial light modulator.

Fig. 23 is a schematic diagram illustrating beam forming based on a cylindrical lens.

Fig. 24 is a schematic diagram showing beam formation based on a galvanometer scanner.

FIG. 25 is a schematic diagram showing beam formation based on a polygon mirror.

Fig. 26 is a schematic plan view showing a positional relationship between the shielding plate and the glass substrate.

Fig. 27 is a schematic front view showing a positional relationship between the shielding plate and the glass substrate.

Fig. 28 is a schematic plan view of a laser irradiation device according to a second modification of the second embodiment.

Fig. 29 is a schematic front view of the laser irradiation device.

Fig. 30 is a schematic diagram showing a three-point beam.

Fig. 31 is a graph showing changes in laser pulse and ray angle with respect to time.

Fig. 32 is a schematic plan view of a conventional glass product formed integrally with a material having low heat resistance.

Description of reference numerals:

a laser irradiation device; a laser device; a transmission optical system; a machining table; a control section; a drive mechanism; a table driving section; a laser oscillator; a laser control section; a condenser lens; an end face; a portion near the end face; a substrate cooling device; a cylindrical lens; a galvanometer scanner; 45.. polygon mirror; a shield plate; a glass substrate; s.. laser facula; a residual stress generating region.

Detailed Description

1. First embodiment

(1) Laser irradiation device

Fig. 1 shows an overall configuration of a laser irradiation device 1 according to an embodiment of the present invention. Fig. 1 is a schematic view of a laser irradiation apparatus according to a first embodiment of the present invention.

The laser irradiation device 1 has a function of reducing the residual stress of the glass substrate G by heating a portion having a high residual stress.

The glass substrate G includes a portion made of glass alone and a portion made of glass combined with another material such as resin. Typical examples of the type of glass include sodium glass and alkali-free glass used for displays, instrument panels, and the like, but the type is not limited to these. The thickness of the glass is specifically 3mm or less, for example, in the range of 0.004 to 3mm, preferably in the range of 0.2 to 0.4 mm.

The laser irradiation device 1 includes a laser device 3. The laser device 3 includes a laser oscillator 15 for irradiating the glass substrate G with a laser beam and a laser control unit 17. The laser control unit 17 can control the driving of the laser oscillator 15 and the laser power.

The laser device 3 includes a transmission optical system 5 that transmits laser light to a mechanical drive system described later. The transmission optical system 5 includes, for example, a condenser lens 19, a plurality of mirrors (not shown), a prism (not shown), and the like.

The laser irradiation device 1 includes a drive mechanism 11 that changes the size of the laser spot by moving the position of the condenser lens 19 in the optical axis direction.

The laser irradiation device 1 has a processing table 7 on which a glass substrate G is placed. The machining table 7 is moved by a table driving unit 13.

The table driving unit 13 includes a moving device (not shown) for moving the machining table 7 in the horizontal direction with respect to the head (not shown). The moving device is a well-known mechanism having a guide rail, a motor, and the like.

The laser irradiation device 1 includes a control unit 9. The control section 9 is a computer system having a processor (e.g., CPU), a storage device (e.g., ROM, RAM, HDD, SSD, etc.), and various interfaces (e.g., a/D converter, D/a converter, communication interface, etc.). The control unit 9 performs various control operations by executing a program stored in a storage unit (corresponding to a part or all of a storage area of the storage device).

The control unit 9 may be constituted by a single processor, or may be constituted by a plurality of independent processors for respective controls.

The control unit 9 can control the laser control unit 17. The control unit 9 can control the drive mechanism 11. The control unit 9 can control the table driving unit 13.

Although not shown, the control unit 9 is connected to sensors for detecting the size, shape, and position of the glass substrate G, sensors and switches for detecting the state of each device, and an information input device.

(2) Melting and rounding

As an example of the processing for generating the residual stress in the glass substrate G, an operation of performing the fusion rounding of the end face of the glass substrate G will be described with reference to fig. 2 to 4. Fig. 2 is a schematic diagram of a glass substrate showing movement of a laser spot. Fig. 3 is a sectional photograph showing a fusion-rounded glass substrate. Fig. 4 is a graph showing a change in phase retardation (retardation) from the end surface toward the middle side of the molten rounded glass substrate.

As shown in fig. 2, the glass substrate G is irradiated with laser light at a portion 21 near the end face of the glass substrate G, and the laser spot S is further scanned along the end face 20 of the glass substrate G. In this case, the laser spot S is set at a position deviated from the end face 20 of the glass substrate G toward the inner side (middle side) of the substrate by, for example, 10 μm to 150 μm.

By performing the irradiation and scanning of the laser spot S as described above, the portion 21 near the end face of the glass substrate G is heated. In particular, by irradiating the laser light of the mid-infrared light, the laser light is transmitted to the inside of the glass substrate G while being absorbed. Therefore, the end surface 20 of the glass substrate G is heated not only on the front side, which is the laser irradiation surface, but also relatively uniformly throughout the inside and the back side of the glass substrate G. Therefore, the end face 20 of the glass substrate G is melted so as to expand outward from the center of the substrate thickness, and as a result, the end face 20 is rounded as shown in fig. 3.

As a result, as shown in fig. 4, the phase retardation (nm) increases in the vicinity of the end face of the glass substrate G (for example, in the region of 200 μm from the end face 20). The phase retardation is a phase difference generated by light transmitted through an object, and is a value proportional to a stress applied to the inside of the object. The increase in the phase retardation of the object to which the external force is not applied means an increase in the residual stress.

(3) Residual stress reduction treatment

The residual stress reduction process will be described with reference to fig. 5 to 8. Fig. 5 to 8 are schematic diagrams of glass substrates illustrating the movement of the laser spot according to the first embodiment.

In fig. 5, the laser spot S1 is irradiated to a point on the end face vicinity portion 21.

In fig. 6, the laser spot S2 is irradiated to another point at a different position on the end face vicinity portion 21.

In fig. 7, the laser spot S3 is irradiated to another point at a different position on the end face vicinity portion 21.

In fig. 8, the laser spot S4 is irradiated to another point at a different position on the end face vicinity portion 21.

When a laser spot is irradiated to a point on the residual stress generation region Z for a predetermined time and heated to a glass transition point or higher, the residual stress is reduced in the region. Therefore, as can be seen from fig. 5 to 8, the processing of heating the one point for a predetermined time is performed line by line, and the laser spots S1 to S4 are irradiated to the positions continuously adjacent in the end face direction, and as a result, the entire end face vicinity portion 21 is irradiated.

However, the number, position, and irradiation order of the laser spots and the ratio of the laser spots in the end surface vicinity portion 21 are not limited to those in the present embodiment.

In this embodiment, the residual stress generation region Z (shaded region) is heated to a temperature equal to or higher than the glass transition point by repeating the operation of heating a single point for a predetermined time and shifting the position and then heating a single point for a predetermined time, thereby reducing the residual stress in the entire end surface vicinity portion 21.

In this embodiment, finally, the laser spot S irradiates the entire end face vicinity portion 21, reducing the residual stress of the entire end face vicinity portion 21. However, when the residual stress is reduced only in a local region in the end face vicinity portion 21, the laser spot S may be irradiated only in a specific region in the end face vicinity portion 21, or may be irradiated only in a region of about half of the entire end face vicinity portion 21.

(4) Shape of laser spot in residual stress reduction treatment

The inventors of the present invention have found based on experiments that in the residual stress reduction treatment, the region that becomes high in temperature needs to be suppressed within a narrow range in the direction along the end face 20, and have thus proposed the present invention.

In this embodiment, a point on the end face vicinity portion 21 is heated for a predetermined time, thereby reducing the residual stress of the heated region. Fig. 9, 10, and 11 are schematic plan views showing changes in the shape of the laser spot S.

Fig. 9 shows a circular laser spot S100 and an elliptical laser spot S101 that is long in the direction orthogonal to the end face 20. Fig. 10 shows the laser spots S102, S103 as oblong laser spots along the end face 20. Fig. 11 shows a laser spot S104 that covers the entire end face 20 and is of a longer shape along the end face 20. In the case where the laser spots S100, S101, S102, S103 are used, if the laser output and the predetermined time for heating are adjusted, the residual stress in the heating area is reduced. Wherein the residual stress reduction effect is improved in the order of S100 ≈ S101 > S102 > S103. In the case where the laser spot S104 is used, the residual stress is not decreased even if the laser output and the predetermined time for heating are adjusted.

In view of the experimental results shown above, the inventors of the present invention have found that in the residual stress reduction treatment, when the shape of the heating domain is formed longer along the residual stress generating region Z, the effect of reducing the residual stress becomes lower, and when the shape of the heating domain is suppressed narrower along the residual stress generating region Z, the effect of reducing the residual stress is improved, and thus have come to propose the present invention.

When the laser spot S is circular, it is preferable that the diameter is, for example, 4 μm to 20 mm. The larger the diameter of the laser spot S, the larger the processing area per heating, and the time required for reducing the residual stress of a predetermined area can be shortened. As shown in fig. 9 and 10, the laser spot S may also be elliptical. The larger the width of the laser spot S in the direction along the end face 20 is, the larger the width of the laser spot S in the direction intersecting the end face 20 is, and the lower the residual stress reduction effect is. Preferably, the width of the laser spot S in the direction along the end face 20 is 10 times or less the width of the laser spot S in the direction intersecting the end face 20.

The predetermined time for heating depends on the temperature of the heating field in heating. In other words, the residual stress can be reduced in a short time by increasing the temperature of the heating region as the heating is performed at a higher output. The longer the heating is performed at a high output, the shorter the predetermined time for heating, and the shorter the tact time (tact time).

Preferably, the predetermined time for heating is, for example, about 1 picosecond to about 100 seconds. The minimum predetermined time is 1 picosecond which is known as the minimum value of the time required for the structure of the glass to relax (relaxation time). The lower the temperature of the heating region, the longer the relaxation time, and when the temperature of the heating region is around the glass transition point, the predetermined time for heating is preferably set to about 100 seconds as the relaxation time.

In order to greatly shorten the predetermined time for heating, it is necessary to heat the glass substrate G to a high temperature in a short time, and the required output is greatly increased, so that in practical use, the heating condition is determined while taking into account the advantage of shortening the tact time and the cost increase due to the increase in output.

The laser output needs to be a value that can be heated above the glass transfer point. It can be set appropriately according to the size of the laser spot, the laser wavelength, the kind and thickness of the glass. When the temperature of the heating portion of the glass substrate G is about the glass transition point, the deformation of the heating portion is hardly confirmed. When the temperature of the heating portion is higher, the heating portion melts and changes in shape. The higher the laser output, the lower the viscosity of the heating portion, and the larger the deformation occurs in a short time. According to the present invention, even when the laser output is high and the shape of the glass substrate G is deformed, the residual stress can be reduced. However, when the present invention is applied to a product in which the allowable deformation amount of the glass substrate G is limited, it is necessary to set the upper limit of the laser output so as to prevent the viscosity of the glass substrate G from being lowered and the deformation amount from exceeding the allowable value.

An example of the condition for heating the alkali-free glass having a thickness of 200 μm for a predetermined time will be described. CO with 4mm laser spot ₂ Laser (wavelength 10.6 μm), 3W, 20 s. The conditions may be 4W and 4 s. The conditions may be 6W and 2 s.

The heat source is not limited to laser light, and may be an infrared heater or a contact heater, for example.

The type (wavelength) of the laser light is not particularly limited.

The direction of heat input to the glass substrate G is not particularly limited. Heat may be input from the front surface of the glass substrate G, from the back surface, or from the end surface 20.

In the above embodiment, the residual stress reduction processing is performed after the completion of the fusion rounding, but the fusion rounding processing and the residual stress reduction processing may be performed in parallel on one glass substrate G. Specifically, by using two laser beams, the residual stress reduction process is started in the middle of the melting rounding operation, and thereafter, the two processes are performed simultaneously. In this case, the entire processing time is shortened.

In order to use a plurality of laser beams, a plurality of laser oscillators may be provided, or a laser beam may be branched from one laser oscillator.

By the above processing, the end surface vicinity portion 21 of the glass substrate G (in other words, the residual stress generation region Z) is heated to a temperature equal to or higher than the glass transition point, and as a result, the residual stress is reduced.

In this method, the end face vicinity portion 21 of the glass substrate G is heated (in other words, not the entire glass substrate G is heated), so that the residual stress of the end face vicinity portion 21 of the glass substrate G formed integrally with a material having low heat resistance such as resin can be reduced. This is because the resin or the like is not easily affected by heat. Further, since the residual stress can be reduced in the heating region by heating the glass substrate for about 1 picosecond to 100 seconds and performing the heating once or a plurality of times with shifting the heating position, the residual stress can be reduced before the occurrence of the breakage even for the glass substrate in which the breakage occurs in usually several tens of minutes due to the high residual stress.

(5) Staggered irradiation mode of laser spots

When the above-described heating method is performed while shifting the positions, the first heating, the second heating by shifting, the third heating by shifting, and the predetermined-time heating … are sequentially performed. In this case, in order to shorten the tact time, the time interval between the heating operations needs to be shortened. However, for example, in the order of heating positions shown in fig. 12, the region adjacent to the last heating region becomes the next heating region. In this case, for example, the temperature of the heating portion decreases until the first heating is required for the second heating. This is because, for example, the second heating region and the first heating region are merged and correspond to the above-described "case where the shape of the heating region is formed long along the residual stress generation region Z".

(5-1) first mode

In the case of the offset irradiation, as a first mode for shortening the time interval between the heating operations, there is a mode in which the heating positions are sequentially changed. Specifically, in this method, as shown in fig. 13, a region adjacent to the previous heating region is skipped and the divided region is set as the next heating region.

(5-2) second mode

As a second mode for shortening the time interval between the heating operations, there is a substrate cooling mode. Fig. 14 shows a substrate cooling device 35 for cooling a glass substrate G by jetting a gas from the front or back surface side of the substrate. Fig. 14 is a schematic view of a laser irradiation device according to a modification of the first embodiment.

In this case, after the first heating zone is cooled by air cooling or the like, the heating is performed for the second time. This can shorten the time interval even when heating is performed in the order shown in fig. 12.

The time interval can be shortened in the above manner because the portion heated by the irradiation of the laser light is cooled and then irradiated with the next laser light, and therefore even if the portion heated before is irradiated with the next laser light, the region that becomes high in temperature is not expanded in the direction along the end face by cooling. In other words, this is because this case corresponds to the above-described "the shape of the heating domain is suppressed to be narrow along the residual stress generating region Z".

The cooling medium used for cooling is not particularly limited.

The substrate cooling device may be realized by setting a stage on which glass is placed as a water-cooled stage.

The substrate cooling mechanism may be mounted on the laser irradiation device 1.

2. Second embodiment

The predetermined-time heating method of the first embodiment employs a one-point heating method in which laser light is irradiated to each point, but laser light irradiation may be performed to a plurality of points at the same time.

Such an example will be described as a second embodiment with reference to fig. 15 to 18. In the multi-spot simultaneous irradiation method, the actual processing speed is increased. Fig. 15 to 18 are schematic views of a glass substrate illustrating movement of a laser spot in the second embodiment.

In fig. 15, two laser spots S1 are irradiated to the end surface vicinity portion 21.

Fig. 16 shows a state in which the residual stress is reduced in the end face vicinity portion 21 by the operation of fig. 15.

In fig. 17, two laser spots S2 are irradiated to the end surface vicinity portion 21. At this time, the two laser spots S2 are irradiated at different positions from the two laser spots S1, that is, with a shift. In addition, two laser spots S2 correspond to the remaining residual stress generation regions Z.

In fig. 18, a situation is shown in which the residual stress is reduced in the end face vicinity portion 21 by the operation of fig. 17.

In the multipoint simultaneous heating method, when the number of heating regions is n points, n times of output is required as compared with the one-point heating method of the first embodiment. In the masking method described later, a higher output is required depending on the area of the masking portion.

The heating conditions for each point are the same as those in the first embodiment.

The interval between the heating zones is preferably 0.5 times or more the width of one point of the heating zone. If the interval between the heating regions is too narrow, a plurality of heating regions are connected, as in the case of irradiating one laser spot long along the residual stress generating region Z. In other words, the residual stress reduction effect is reduced in correspondence with the above-described "case where the shape of the heating domain is formed long along the residual stress generating region Z". Fig. 20 shows a change in the shape and the interval of the heating region using fig. 19. Fig. 19 and 20 are schematic plan views showing changes in the shape and the interval of the heating regions.

A three-point circular laser spot S105 is shown in fig. 19. The laser spot S105 has the same shape as the laser spot S100 in fig. 9, and the residual stress reduction effect is high. The interval between the laser spots S105 is set to be substantially the same as the width of the laser spot S105.

Fig. 20 shows an elliptical three-point laser spot S106 that is long in the direction intersecting the end face 20. The laser spot S106 has the same shape as the laser spot S101 in fig. 9, and the residual stress reduction effect is high. The interval of the laser spot S106 is set to be substantially the same as the width of the laser spot S106.

In addition to the above, there are many combinations of laser spot shapes and spacings.

The processing speed of the residual stress reduction processing varies depending on the number of heating areas. For example, when the width of the heating zones is 8mm, ten-point simultaneous heating is performed, the heating time is 1s, and the residual stress reduction width per heating zone is 4mm, the processing speed of one irradiation is 4mm × 10/1s, which is 40 mm/s.

A mode of performing simultaneous multipoint heating by the optical branching element will be described with reference to fig. 21 and 22. Fig. 21 is a schematic diagram showing branching of laser spots using a diffractive optical element or a transmissive spatial light modulator. Fig. 22 is a schematic diagram showing branching of a laser spot using a reflective spatial light modulator.

In fig. 21, a Diffractive Optical Element (DOE) 31 or a transmissive Spatial Light Modulator (SLM) 31 is shown.

In fig. 22, a reflective Spatial Light Modulator (SLM)33 is shown. In addition, two mirrors 34 are shown.

In the case of performing the multipoint simultaneous heating method shown in fig. 15 to 18 while shifting the position, the first heating, the second heating by shifting, the third heating by shifting, and the … heating for a predetermined time are performed sequentially. In this case, in order to shorten the tact time, the time interval between the heating operations needs to be shortened. However, for example, when any of the plurality of second heating areas is adjacent to any of the plurality of first heating areas, the second heating needs to wait until the temperature of the first heating unit drops. This is because, for example, the second heating region and the first heating region are merged and correspond to the above-described "case where the shape of the heating region is formed long along the residual stress generating region".

As a first aspect of shortening the time interval between the heating operations, in the above case, the heating position is sequentially changed to a position where the second heating region is distant from the first heating region, thereby shortening the time interval.

As a second mode for shortening the time interval between the heating operations, there is a substrate cooling mode. In this embodiment, as shown in fig. 14 of the first embodiment, a substrate cooling device 35 is used which cools the substrate G by jetting gas from the front side or the back side of the substrate G. In this case, the heating is performed for the second time after the first heating region is cooled by air cooling. This can shorten the time interval even when the second heating zone is adjacent to the first heating zone, for example.

The time interval can be shortened in the above manner because the portion heated by the irradiation of the laser light is cooled and then irradiated with the next laser light, and therefore even if the portion heated before is irradiated with the next laser light, the region that becomes high in temperature is not expanded in the direction along the end face by cooling. In other words, this is because this case corresponds to the above-described "case where the shape of the heating domain is suppressed to be narrower along the residual stress generation region".

The cooling may be performed at normal times, or may be performed after the laser light is irradiated.

As in the first embodiment, the structure, cooling unit, and arrangement position of the cooling device are not particularly limited.

(1) First modification

A method of performing multipoint simultaneous heating by a shielding method will be described with reference to fig. 23 to 27. Fig. 23 is a schematic diagram illustrating beam forming based on a cylindrical lens. Fig. 24 is a schematic diagram showing beam formation based on a galvano scanner (galvano scanner). FIG. 25 is a schematic diagram showing beam formation based on a polygon mirror. Fig. 26 is a schematic plan view showing a positional relationship between the shielding plate and the glass substrate. Fig. 27 is a schematic front view showing a positional relationship between the shielding plate and the glass substrate.

The light beam having an elongated shape along the end face 20 is formed by the cylindrical lens 41 (fig. 23), the galvanometer scanner 43 (fig. 24), the polygon mirror 45 (fig. 25), and the like.

Thereafter, as shown in fig. 26 and 27, the laser beam B is partially shielded by the shielding plate 47, thereby forming a plurality of laser spots S. The shielding plate 47 has a plurality of shielding portions 47a arranged with gaps therebetween in the end surface direction.

The shielding plate 47 needs to reflect or absorb the laser light. In the case of absorption, heat resistance is required. If the laser beam does not have sufficient heat resistance to absorb the laser beam, a forced cooling mechanism including a shielding plate is required.

A mechanism (not shown) for moving the shielding plate 47 along the end face vicinity portion 21 of the glass substrate G may be provided. In this case, the positions of the plurality of laser spots S can be changed, and the laser spots S can be irradiated to the entire end surface vicinity portion 21 by repeating this process.

(2) Second modification example

A method of performing multipoint simultaneous heating so as to perform one laser scanning with one pulse will be described with reference to fig. 28 to 31. Fig. 28 is a schematic plan view of a laser irradiation device according to a second modification of the second embodiment. Fig. 29 is a schematic front view of the laser irradiation device. Fig. 30 is a schematic diagram showing the formation of a three-point laser spot using the galvanometer scanner 43. Fig. 31 is a graph showing changes in laser pulse and ray angle with respect to time.

As shown in fig. 28 and 29, the laser irradiation device 1A includes a laser oscillator 15, a beam expander 49, a condenser lens 19, and a galvanometer scanner 43. The laser irradiation device 1A controls the position of each pulse of the laser light using the galvanometer scanner 43, and irradiates the laser light to a plurality of places at approximately the same time, thereby producing a state in which a plurality of spots are heated at the same time.

In the example of fig. 30, the ray angle of the laser beam was changed by 1 ° by the galvanometer scanner so that the position of the laser spot was shifted by 10mm on the sample surface. As shown in fig. 31, when the light angle is changed in synchronization with the laser pulse oscillated at 500Hz, the laser light makes one round trip in a region of 20mm in a period of 12 milliseconds, and the laser spots at three points are irradiated with the laser light for 2 milliseconds in one period (12 milliseconds), respectively. In addition, the laser light does not irradiate the region between the three laser spots. In this case, the period of laser scanning is very fast, and therefore if this operation is repeatedly continued for a predetermined time (for example, for 1 second), the three points are simultaneously heated for a predetermined time.

As shown in fig. 29, a substrate cooling device 35 is provided in the second modification. However, the substrate cooling device may not be provided.

3. Other embodiments

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. In particular, the plurality of embodiments and the modifications described in the present specification can be arbitrarily combined as needed.

The present invention is also applicable to a case where the melting rounding is not performed.

The present invention is also applicable to a case where the residual stress generating region is not in the vicinity of the end face of the glass substrate G but, for example, in the middle portion.

Industrial applicability of the invention

The present invention can be widely applied to a residual stress reduction method for a glass substrate and a residual stress reduction device for a glass substrate.

Claims

1. A method for reducing residual stress of a glass substrate, which is a glass substrate that is not subjected to edge finishing and is separated by forming a scribing line on the glass substrate before cutting by a cutter wheel and cutting along the scribing line, wherein,

the method for reducing residual stress of a glass substrate includes a laser irradiation step of heating the glass substrate by irradiating a plurality of places of the glass substrate where residual stress is high with laser light for a predetermined time.

2. The method for reducing residual stress of a glass substrate according to claim 1,

in the laser irradiation step, a plurality of laser beams are simultaneously irradiated to the plurality of places.

3. The method for reducing residual stress of a glass substrate according to claim 1 or 2,

in the laser irradiation step, laser irradiation is repeated for different locations.

4. The method for reducing residual stress of a glass substrate according to claim 1,

in the laser irradiation step, the heating is performed by irradiating each of the plurality of places with the laser light for 1 picosecond to 100 seconds.

5. A residual stress reducing device for a glass substrate, which reduces the residual stress of the glass substrate that is not subjected to edge finishing and is separated by forming a scribing line on the glass substrate before cutting by a cutter wheel and cutting along the scribing line,

the residual stress reduction device for a glass substrate is provided with a laser device that heats a plurality of places of a high residual stress portion of the glass substrate by irradiating the places with laser light for a predetermined time.

6. The residual stress reduction device for glass substrates according to claim 5,

the laser device irradiates a plurality of laser beams to the plurality of places simultaneously.

7. The residual stress reduction device for glass substrates according to claim 5 or 6,

the laser device repeatedly performs laser irradiation to different places.

8. The glass substrate residual stress reducing apparatus according to claim 5,

the laser device heats the plurality of portions by irradiating the plurality of portions with the laser beam for 1 picosecond to 100 seconds.